Definition of migration in English:

noun

This may be an important mechanism promoting the shoreward migration of larval invertebrates and fish.

In proposing the waiver, the agency suggested that it would actually benefit wildlife: By interrupting migration, drilling would enable scientists to study the effects of habitat disruption on the deer.

But each year the number decreased until there was only one, which left in late February, 1995, to begin its long spring migration to Russia's steppes.